In conventional image forming apparatuses exploiting electrophotography, a charging device is incorporated for electrostatically charging the surface of a photosensitive member which is an image carrying member. There are known charging devices of a corona charging type in which a photosensitive member and a corona wire are arranged with no contact with each other to electrostatically charge the surface of the photosensitive member by corona discharge, and charging devices of a contact charging type in which contact is made with the surface of a photosensitive member by use of a charging member such as a charging roller. However, in recent years, to reduce the amount of discharged ozone, which is harmful to the human body, the contact charging-type charging devices, which discharge less ozone, have been increasingly used.
When a charging roller is brought into contact with the surface of a photosensitive member in such a contact charging-type charging device, foreign matter such as a toner component or paper dust of sheets may attach to the surface of the photosensitive member, and the foreign matter may move to the surface of the charging roller. The foreign matter attached to the surface of the charging roller causes failure to electrostatically charge the surface of the photosensitive member, greatly affecting the image quality of images printed. To prevent the foreign matter from attaching to the charging roller as described above, conventionally, by bringing a cleaning member such as a cleaning brush or a cleaning roller into contact with the surface of the charging roller, the foreign matter attached to the charging roller is removed.
For example, Patent Document 1 discloses an image forming apparatus in which a cleaning roller in pressed contact with the circumferential surface of a charging roller is driven to rotate while keeping a linear velocity difference relative to the charging roller, and the cleaning roller reciprocates in the axial direction of the charging roller so that soil on the charging roller is removed.